Question

The following data is the result of a controlled laboratory experiment on the relative effects of salinity (percentage of pure seawater, 32 parts per 1000) on the respiration rate (U/L O2/ g/ hr) of two different species of starfish. (Source: J. Houston, Dept. of Zoology, Univ. of Guelph.)

Species	Asterias vularis				Asterias forbesis
Salinity (%)	20	50	90		20	50	90
	27.23	25.34	14.42		24.92	18.9	9.94
	29.54	27.65	14.48		23.87	23.94	8.32
	34.3	21.35	14.63		26.46	21.77	9.64
	28.21	25.41	18.69		22.26	20.02	12.76
	30.17	22.54	12.39		25.55	20.39	10.4

Do a COMPLETE test on this data.

Answer 1

Two-way ANOVA: result versus salinity, species

Source DF SS MS F P
salinity 2 1131.19 565.595 121.35 0.000
species 1 150.57 150.573 32.31 0.000
Interaction 2 4.36 2.178 0.47 0.632
Error 24 111.86 4.661
Total 29 1397.98

S = 2.159 R-Sq = 92.00% R-Sq(adj) = 90.33%

We have performed two-way ANOVA here.Two factors are species and salinity which have two and three levels respectively.Again if we consider interaction then large p-value indicates there is no interaction effects in this experiments, whereas main effects of each factor individually has a significant effect here.Moreover this model is quite appropriate due to high value of R sq.92% of total variances are explained through these factors in this two-way model.